Method of manufacturing rotating commutators, particularly adapted for automatic machine assembly

ABSTRACT

A continuous strip of conductive material, for example copper, bronze, aluminum or the like is provided having, in alternate sections, the cross-sectional shape of commutator segments (channel-shaped, T-shaped, L-shaped, C-shaped), and rod-like connecting strips, preferably half, or less the thickness of the commutator segments. A ring-shaped mold is provided, having segmental steel inserts separated by separator strips of blued steel; the steel inserts form guide ways for the segments, which are pushed in, severed at the far end of the connecting strip, and the mold is then indexed to the next guide way position accepting a commutator segment from the continuous strip. The commutator ring is then secured together by molding plastic in the spaces between the commutator segments, as known, or are otherwise locked together for example by means of insulating spacer shims inserted between the segments, and the mold pressed together.

United States Patent Coquard [S4] METHODOF MANUFACTURING ROTATINGCOMMUTATORS, PARTICULARLY ADAPTED FOR AUTOMATIC MACHINE ASSEMBLY [72]Inventor: Lucien Coquard, Asnieres, France [73] Assignee: SocieteIndustrielle de Travaux Electro-Mecaniques (S.I.T.E.M.)

221 Filed: May 14, 1970 21 Appl.No.:37,277

6/1968 Noris ..'...29/597 [451 Dec. 5, 1972 Primary Examiner-Charles W.Lanham Assistant Examiner-Carl E. Hall Attorney- Flynn & Frishauf [57ABSTRACT A continuous strip of conductive material, for example copper,bronze, aluminum or the like is provided having, in alternate sections,the cross-sectional shape of commutator segments (channel-shaped,T-shaped, L-shaped, C-shaped), and rod-like connecting strips,preferably half, or less the thickness of the commutator segments. Aring-shaped mold is provided, having segmental steel inserts separatedby separator strips of blued steel; the steel inserts form guide waysfor the segments, which are pushed in, severed at the far end of theconnecting strip, and the mold is then indexed to the next guide wayposition accepting a commutator segment from the continuous strip. Thecommutator ring is then secured together by molding plastic in thespaces between the commutator segments, as known, or are otherwiselocked together for example by means of insulating spacer shims insertedbetween the segments, and the mold pressed together.

8 Claims, 6 Drawing Figures PATENTEDnEc 5 I972 3,704,513,

SHEET 3 BF 3 ma'rnon or MANUFACTURING ROTATING CQMMUTATORS, PARTICULARLYADAPTED roa AUTOMATIC MACHINE ASSEMBLY commutators for dynamo-electricmachines of small size, such as commutators having an overall diameterof 4 centimeters, or less, although the method is applicable tocommutators of all sizes." I

Ordinarily, commutators. of dynamo-electric machines consist of acircular assembly of copper, or other electrically conductive strips,insulated from each other and secured to a ring shaped carrier. Thecommutator segments are, in accordance with one method of theirmanufacture, first cut to have, in the longitudinal direction of thecommutator, the profile desired for assembly. The width' of the stripscorresponds to an angle of 360, divided by' the number of commutatorsegments, less the width of one insulating gap. The commutator segmentsare assembled in a circle, separated one from the other by insulatingstrips, for example mica or the like. Thereafter, the entire assembly isrigidly secured together, for example by rings, clamps, or other lockingarrangements; they may also be secured by connecting them together inaplastic molding material. Collectors which utilize plastic moldingmaterial may be assembled without first inserting the insulatingspacers, since the plastic molding material can be injected to fill inthe gap between the collector segments. The commutator is then assembledto the shaft of the dynamo-electric machine'and later connected to thewindings of the rotor. Connection to the windings of the rotor is byterminals which may have the form of taps, pigtail extensions, loops forinsertion of wires from a rotor, or other structure to be commutated, orthe like.

Commutators of this type are made in large quantities, and it isdesirable to completely automate their manufacture. Simulating the handassembly of commutators is not, however, suitable since mechanicalapparatus to grasp the collector segments and placing them on a mountingringis cumbersome, particularly when small commutators are involved.Furthermore, in the final method steps, complicated and easilymaladjusted equipment is necessary in order to provide terminal elementsto connect the collector to other circuit components, for example thewindings of a rotor.

It is an object of the present invention toprovide a method, andapparatus and sub-assembly components to carry out the method tomanufacture, automatically, commutators, and more particularlycommutators which are molded and which further provide terminal elementssuch as lugs, loops, or the like for connection to other electricalcomponents, for example rotor windings.

Subject matter of the present invention Briefly, a continuous strip ofmaterial is formed having, in alternate sections, the cross-sectionalshape, and length of commutator segments, and connectingstrips whichpreferably are rod-like, that is of square or circular cross-section,and of half or less the thickness of the commutator segments. Thiscontinuous strip of alternate commutator and connecting strip sectionsisfed towards a fixture which is in the form of an open ring and has, atits innersurface, locating dividers forming locating arrangements tolocate commutator segments. The commutator segments are pushed, inproper l0cation, into the mold and a cutter then cuts off the connectingstrips close to, or flush with the beginning of the next adjacentcommutator segments, the cutter simultaneously forming the connectingstrip to form a terminal end, or lug, for example in ring shape, forconnection to electrical components, such as the windings of a rotor.The moldisthen indexed to the next subsequent commutator position, andthe process repeated. When the entire mold is filled with commutatorsegments, it is placed in a plastic molding injection apparatus, ofknown and customary type, for example supplied with a mandrel, to moldthe commutator segments into a ring-commutator forassembly on a shaft;or, the mold can be directly placed over an already assembled rotorshaft and the commutator molded directly on theshaft of adynamo-electric machine.

If desired, divider strips may be inserted between the commutatorsegments; this, also, can be dome automatically, the feed of thecontinuous strip of commuta tor and connection strip material, and theinsulating strips being synchronized.

In accordance with a feature of the invention, a strip of material isprovided which in alternate sections provides the commutator segmentsand the connecting strips.

In accordance with another feature of the invention, a mold or die isprovided which is ring-shaped and contains therein sector-shaped insertsof generally trapezoidal cross-section, with the parallel sides of thetrapezoid being rounded to match the curvature of the corn: mutator, thesections being divided by thin plates of blued steels, spring steel, orthe like which project slightly beyond the segmental, trapezoidalpieces, to form guide ways for insertion of the commutator segments.These pieces are easily machined and manufactured, in substantialquantities and in various sizes to provide molds which, themselves, areinexpensive, so that a large number of commutators can inexpensively bemade. i a

The invention will be described by way of example with reference to theaccompanying drawings, wherein:

I FIG. 1 illustrates various shapes of commutator elements, in endviews;

FIG. 2 is a perspective view of a continuous strip of commutatorsegments and connecting strips;

FIG. 3 is a fragmentary, perspective view showing insertion ofcommutator segments and an assembled segment with a formed terminalloop;

FIGS. 4 and 5 are fragmentary schematic side views, partly incross-section, illustrating sequential steps in insertion commutatorsegments, forming of terminal strips, and severing of individualsegment-strip elements;

FIG. 6 is a fragmentary end view illustrating one type of die or moldfor use in the process.

Any type of commutator may be made in accordance with the presentinvention. It is, however, particularly applicable to high-volumeproduction for small commutators of the molded type, having a diameterin the order of 4 centimeters (about I% inch) or less and having 20, orless individual commutator segments. The shape of the commutatorsegments is left to the choice of the designer of the commutator, andmay have any desired shape, several customary and well known shapesbeing shown in FIG. 1 at a (arc-shaped); b (T-shaped); c (Id-shaped);and d (C-shaped). Each of these shapes has a profile which has a roundedouter partially cylindrical surface to match the circle of rotation ofthe commutator. The outer part of the collector segment is approximatelytrapezoidal in cross-section, followed by a converging region which, inelement c of FIG. I may be defined by the next adjacent commutatorsegment, so that the base of the particular commutator segment will besmaller than the outside so that the segments themselves will besecurely held and locked together by plastic material moldedtherearound. The segments themselves can be separated either by themolded plastic material, by additional separating strips, or by both.

In accordance with the present invention, the collector segments whichmay have any one of the shapes of FIG. I are formed as a continuousstrip of material of copper, or' any other commutator material which,alternately, is followed by a connecting strip or lesser cross-sectionalsize, as best seen in FIG. 3. The entire assembly band, or strip, withthe connecting strips shown exaggerated, is seen in FIG. 2, where thecollector segments 1 are interconnected by connecting strips 2. Theinterconnecting strips should be of such crosssectionthat they canreadily be severed by a cutter, a punch, or similar element, and theymay be in rod-like form, round, rectangular or square in cross-sectionand preferably with a cross-sectional size half, or less than thethickness of the outer portion of the collector segments. Their lengthis, preferably, equal to, or less than the length of a collectorsegment. Manufacture of such strips is simple, requires only smallstocking or storage areas and can readily be stored in coil form, forwinding off a-turret, or in long longitudinal strips.

FIG. 3 illustrates the insertion of commutator segments. A jig, in formof a mold 4 is provided which has guide ways 3, separated from eachother by ridges 5. The guide ways 3 form guides for positioning of thecommutator segments I, pushed between the ridges 5. Ridges 5 provide forspacing of the collector segments,

so that insulating material can flow therearound to separate thecollector segments and insulate them from each other. The number of theguide ways is equal to the number of the commutator segments. The heightof the separating ridges 5 is as small as consistent with goodpositioning, in view of manufacturing processing speed, that is justsufficient to hold the commutator segments in place, and leaving themajor extent of the space between the commutator segments free forplacement of resin during molding of the commutator.

Collector segment I, seen pushed in position, abuts a reinforcement ring6 at the inner end of the ring-shaped jig, or fixture 4. Afterpositioning a commutator segmerit, as seen in FIG. 3, the connectingstrip 2 is cut just at, and preferably flush with the end of the nextsucceeding commutator segment to be placed in position. During, or afterthe cutting, the connecting strip is shaped to form a terminal; it maybe split, or, if sufficiently long, bent over a small projecting ring 8formed on fixture 4, to form a terminal loop 7. During the cuttingoperation, the connecting strip 2 may e given any desired shape or form;rather than being formed into a loop, or split for a pinch connection,the connecting strip may be entirely cut, it may be angled off, left asa straight lug, or be given any other form.

After assembling all the commutator segments, the die is put into amolding press in order to seal and lock the commutator segments by aplastic resin, in accordance with known manufacturing processes. Amandrel may be used if the commutator is formed separately, bearings canbe molded inside of the commutator, or the commutator can be moldeddirectly on a shaft.

The exterior surface of the mold 4 is preferably conical, so that it canreadily be centered in a holder, and afterwards in a molding press.FIGS. 4 and 5 illustrate sequential steps in the process ofautomatically manufacturing a commutator. A table 10 supports acontinuous strip of commutator segments, separated by the connectingstrips 2. The mold 4, only a portion of the interior of which is shownin FIGS. 4 and 5, is aligned with an injection opening on table 10, themold 4 being held in a conical holder 13 which can be indexedcircumferentially. A pusher 11 pushes a segment into the mold 4, untilthe commutator segment strikes abutment ring 6. Cutter 12 then movesdownwardly, cutting connecting strip 2 and simultaneously forming it tobe bent over the ridge 8 (see FIG. 5). The cutter, and the ridge 8, canbe shaped to provide a different form of terminal end. Thereafter, thecutter will retract, holder 13 index by one circumferential position,push element 11, having retracted during the cutting operation, willadvance the strip of material forming the commutator segments andconnecting strips to be inserted in the next, indexed position mold 4.Alignment of the mold with the insertion motion of strip 1, 2, issimple.

The mold itself can readily be manufactured, with inserts which can bechanged to accommodate different commutators, of different sizes andhaving different numbers of elements. As seen in FIG. 6, a ring-shapedholder 14 has located therein inserts, the end view of which isgenerally trapeze-shaped, with rounded sides, and made, for example, ofsteel. The inserts 16 are separated from each other by divider strips15, for example of blue steel, spring steel, or the like, extendingslightly beyond the outline of units 16 shown exaggerated in FIG. 6. Thespace between inserts 15 then forms the guide way, positioning thecommutator seg ments. The angle of the converging sides of unit 16 isapproximately equal to 360 divided by the number of commutator segmentsto be assembled; the insert and separator strips 15 are usually so thin,in comparison to the width of units 16, that they can be parallel.

The invention has been described in connection with assembly of acommutator in which the individual commutator segments are separated andinsulated from each other by molded material. It is, of course, equallypossible to insert manually, or automatically, insulating strips betweenthe commutator segments themselves. These insulator strips can beinserted simultaneously, or subsequent to the insertion of thecommutator segments themselves (FIGS. 4 and 5) at the same, or adifferent insertion station and in a similar manner, being cut off,however, flush with the commutator by a knife manna MI '1 passing onlyto the depth of the commutator segments, or extending therebeyond, asdesired by the designer of the commutator. Such insulating strips may beof mica, insulating board or other material. To lock the assemblytogether, the group of assembled commutator segments can be then beplaced in a ring which is slightly smaller than that of the assemblyring 4, so that the commutator will form one unitary whole.

Claims: 1. Method of manufacturing rotating commutators having aplurality of commutator segments secured together, particularly adaptedfor automatic machine assembly comprising forming a continuous strip ofmaterial having spaced, repetitive segments formed in thecross-sectional shape, and length of the commutator segments (1) andconnecting strips (2) connecting adjacent ones of said segments,

providing a mold (4) in ring form having an internal openingcorresponding approximately to the final outer diameter of thecommutator, the inner opening of said mold being formed with locatingmeans for placing and retaining commutator segments in said mold, anddefining commutator segment positions;

inserting one of said segments (1) forming part of said continuous stripinto said mold and in position to be retained by said locating means;

severing the connecting strip (2) attached to the inserted segment atits junction with a subsequent commutator segment;

indexing said mold by one commutator segment position;

repeating said inserting, separating, and indexing steps until allcommutator segment positions in the mold are filled with commutatorsegments to assemble the segments into a complete array of commutatorsegments;

and securing said assembled segments in position relative to each other.

2. Method according to claim ll, wherein said securing step includes thestep of injecting a moldable plastic substance in the mold with saidsegments located therein to fit said segments in position whilesimultaneously insulating said segments from each other.

3. Method according to claim ll, including the step of deforming theconnecting strip into a bent-over portion while severing'the strip froma subsequent commutator segment.

4. Method according to claim 3, wherein the deforming step comprises thestep of forming the connecting strip into a loop.

5. Method according to claim 1, including the step of inserting aninsulating divider strip adjacent said com mutator segment.

6. Method according to claim 1, including the step of inserting, afterassembly of said segments into said mold, insulating divided stripsbetween said segments;

and transferring said assembled segments, with said insulating stripstherebetween, into a mold of smaller size than said first-assembly moldto lock said elements together.

7. Method according to claim 1, wherein said insertion step includes thestep of aligning a commutator position in a predetermined line;

and feeding said commutator segment and connecting strip into the moldalong said line to locate said segment into the mold;

and said indexing step comprises indexing said mold to a commutatorposition not yet filled by a commutator segment.

8. Method according to claim 1, wherein said locating means comprisesridges (5) formed internally of the mold and spaced approximately by thewidth of a commutator segment and leaving between the ridges an open wayto form said commutator position receiving a commutator segment, theridges having a thickness corresponding to the spacing of saidcommutator segments.

1. Method of manufacturing rotating commutators having a plurality ofcommutator segments secured together, particularly adapted for automaticmachine assembly comprising forming a continuous strip of materialhaving spaced, repetitive segments formed in the cross-sectional shape,and length of the commutator segments (1) and connecting strips (2)connecting adjacent ones of said segments; providing a mold (4) in ringform having an internal opening corresponding approximately to the finalouter diameter of the commutator, the inner opening of said mold beingformed with locating mEans for placing and retaining commutator segmentsin said mold, and defining commutator segment positions; inserting oneof said segments (1) forming part of said continuous strip into saidmold and in position to be retained by said locating means; severing theconnecting strip (2) attached to the inserted segment at its junctionwith a subsequent commutator segment; indexing said mold by onecommutator segment position; repeating said inserting, separating, andindexing steps until all commutator segment positions in the mold arefilled with commutator segments to assemble the segments into a completearray of commutator segments; and securing said assembled segments inposition relative to each other.
 2. Method according to claim 1, whereinsaid securing step includes the step of injecting a moldable plasticsubstance in the mold with said segments located therein to fit saidsegments in position while simultaneously insulating said segments fromeach other.
 3. Method according to claim 1, including the step ofdeforming the connecting strip into a bent-over portion while severingthe strip from a subsequent commutator segment.
 4. Method according toclaim 3, wherein the deforming step comprises the step of forming theconnecting strip into a loop.
 5. Method according to claim 1, includingthe step of inserting an insulating divider strip adjacent saidcommutator segment.
 6. Method according to claim 1, including the stepof inserting, after assembly of said segments into said mold, insulatingdivided strips between said segments; and transferring said assembledsegments, with said insulating strips therebetween, into a mold ofsmaller size than said first assembly mold to lock said elementstogether.
 7. Method according to claim 1, wherein said insertion stepincludes the step of aligning a commutator position in a predeterminedline; and feeding said commutator segment and connecting strip into themold along said line to locate said segment into the mold; and saidindexing step comprises indexing said mold to a commutator position notyet filled by a commutator segment.
 8. Method according to claim 1,wherein said locating means comprises ridges (5) formed internally ofthe mold and spaced approximately by the width of a commutator segmentand leaving between the ridges an open way to form said commutatorposition receiving a commutator segment, the ridges having a thicknesscorresponding to the spacing of said commutator segments.